Its code name is PF-07321332, which is currently referred to as « 332 ». It would be even more effective than Merck’s antiviral.
On September 9 (Paris Match n° 3775), we described the very positive preliminary results of molnupiravir, an oral anticoronavirus developed by the American laboratories Merck & Co and Ridgeback Biotherapeutics. This product, which reduces viral load, is to be taken for five days from the first symptoms of infection. Its phase 3 (randomized and double-blind), which concludes the clinical trials prior to possible marketing, has been completed. It shows that in patients who contracted Covid-19, the risk of hospitalization and death (7.3% in the treated group versus 14.1% in the placebo group) is reduced by 50% overall. The response of the American and European drug agencies (FDA and EMA) to Merck’s application to market its product is imminent. France has already ordered 50,000 doses.
Pfizer has just announced that it has also developed an oral antiviral that would be able to reduce the risk of hospitalization and death by 89%. That’s even better! A first analysis, indeed, made after 28 days in 774 recently infected subjects, counted 27 hospitalized or dead people in the placebo group against 3 without death in the treated group. A second analysis of 1,219 patients showed similar results: 41 patients hospitalized or died in the placebo group versus 6, with no deaths, in the treatment group (85% reduction). Pfizer’s product combines two molecules belonging to the class of viral protease inhibitors (enzymes that allow a virus to assemble its proteins, without which it loses its infectious power): 332 itself, a synthetic product created by Pfizer in 2020 whose exact formula is still unknown, and ritonavir, prescribed against the AIDS virus since 1996.
The treatment consists of taking two tablets of 332 and one of ritonavir twice every 24 hours, within the first three days of symptoms and for five days. It could also be given as a preventive measure to people who are particularly exposed to the virus; a study is underway. It would have fewer side effects than molnupiravir (details currently unavailable), no possible impact on cell DNA (which might not be the case with the Merck product) and would not induce viral resistance.
It is highly likely that both drugs will reach the market quickly: as early as the end of this year for molnupiravir and in 2022 for 332 (which Pfizer would then plan to call Paxlovid). The factors that will play a role in the predominance of one or the other will be, for prescribing physicians, their respective adverse effects; for state authorities, their cost; and for patients, their more or less widespread availability in pharmacies. The two American giants seem ready to modulate their prices by country, rich or poor, and to produce on a large scale.
Overall, this is good news. We have repeatedly explained on this page that vaccines, while indispensable, are still insufficient to contain a virus that mutates as much as Sars-CoV-2. And we have also indicated that monoclonal antibodies, which can only be administered by injection and are expensive, can only be used in hospitals for severe forms of the disease. The end of the pandemic is in sight before that point. When 80% of the population of our country is vaccinated – we will be there soon – the risk of severe forms of the virus in those who are immune and contract a variant of the virus (notably Delta, which is currently predominant in the world) will still be reduced by 90% in most cases. If, for the 10% who escape this outcome, oral antivirals are available for a few days, what was an uncontrollable and threatening pandemic will become a permanent epidemic (endemic), evolving at a low level and controllable, like all those we already live with.
Other antivirals than those from Merck and Pfizer will certainly be proposed in the future. The strategy to fight Covid-19 should therefore be simplified: primacy to vaccination, oral antiviral as second line if necessary or first line in non-vaccinated infected people, who will be more and more in the minority. A resurgence of the virus linked to the winter period is well underway, which should still encourage compliance with barrier measures. But the end of the tunnel is probably not far off.